I've got an idea for mounting a folding extension table off the back of
my table saw which starts with bolting an aluminum angle to the cast
iron top. Do I need to worry about electrolysis between the aluminum
and the cast iron?
I don't think so. First, for galvanic corrosion to take place, there has to
be the prescence of an electrolyte, usually water. Second, there's not a
large potential difference between cast iron and aluminum alloys. Even if
it did happen somehow, since aluminum is less noble than cast iron, the
aluminum (aluminium for our friends across the pond) angle would be the
anode and would sacrafice itself, so the table saw top would be protected.
I've been using the same aluminum [aluminium] insert in my cast
iron table top since 1975 and haven't detected any ill effects.
It's probably something not much worth worrying about.
I recently added an outfeed table to my saw - also starting by
attaching an aluminum angle - that you can look over at
<http://www.iedu.com/DeSoto/outfeed.html . It seems to be surviving fairly well (and will probably outlast me!)
Aluminium extrusion is often anodised, which is some of the best
electrolytic protection you could get.
As to the rest, then if it's going to get wet, then you should worry
(there are primers to deal with this). For a saw part in a normal
workshop though, it's no problem.
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